Hybrid vehicles including an engine and a motor/generator have been known. An example of such hybrid vehicles includes a parallel hybrid vehicle (e.g., Patent Document 1). Wheels of the parallel hybrid vehicle are driven only by the motor/generator in, for example, an operating range in which the load is relatively low, whereas the wheels are driven only by the engine or by the engine and the motor/generator in an operating range in which the load is relatively medium and in an operating range in which the load is relatively high. When the speed of the parallel hybrid vehicle is reduced, the vehicle performs regenerative operation by the motor/generator to charge a battery. Even when the wheels of the parallel hybrid vehicle are driven only by the engine, there may be a case where the engine is operated in an operating range in which the load is higher than or equal to a torque required by the vehicle and results in high fuel-consumption efficiency, while the motor/generator is operated by a surplus torque exceeding the torque required by the vehicle, thereby generating power.